How to read an Excel CSV file in Python

Question

data = ['a', 'b', 'c', 'd', 'c', 'd', 'c', 'd']

pattern_counts = {}

for i in range(len(data)-2):
    pattern = str(data[i]) + str(data[i+1]) + str(data[i+2])
    if pattern in pattern_counts:
        pattern_counts[pattern] += 1
    else:
        pattern_counts[pattern] = 1

for pattern, count in pattern_counts.items():
    print("{}: {}".format(pattern, count))

When this code executes, a list of patterns for three value sets is printed. It accomplishes this effectively and precisely.

I want to know how to get it to read an Excel CSV file with vertical values going down.

I've attempted and will continue to try breaking down the code to figure out how to translate it into reading cells.